U.S. patent application number 12/299163 was filed with the patent office on 2009-03-19 for power supply apparatus.
Invention is credited to Izumi Takahashi.
Application Number | 20090075162 12/299163 |
Document ID | / |
Family ID | 39709960 |
Filed Date | 2009-03-19 |
United States Patent
Application |
20090075162 |
Kind Code |
A1 |
Takahashi; Izumi |
March 19, 2009 |
POWER SUPPLY APPARATUS
Abstract
A power supply apparatus wherein a liquid medium is housed so as
to provide an air layer in a first case which accommodates a power
supply unit. When the liquid medium is heated to a temperature
higher than a vaporization temperature by external heat toward the
power supply unit, the liquid medium is vaporized to increase the
volume of the air layer to reduce heat conduction of the external
heat toward the power supply unit. Since this can reduce the heat
conduction of the external heat toward the power supply unit, it is
possible to prevent an extreme increase in temperature of the power
supply unit due to the external heat.
Inventors: |
Takahashi; Izumi; (Aichi,
JP) |
Correspondence
Address: |
KENYON & KENYON LLP
1500 K STREET N.W., SUITE 700
WASHINGTON
DC
20005
US
|
Family ID: |
39709960 |
Appl. No.: |
12/299163 |
Filed: |
February 14, 2008 |
PCT Filed: |
February 14, 2008 |
PCT NO: |
PCT/JP2008/052397 |
371 Date: |
October 31, 2008 |
Current U.S.
Class: |
429/120 |
Current CPC
Class: |
H01M 10/613 20150401;
H01M 10/653 20150401; H01M 10/6554 20150401; H01M 10/625 20150401;
H01M 10/63 20150401; H01M 50/24 20210101; H01M 50/20 20210101; H01M
10/643 20150401; H01M 10/6569 20150401; H01M 10/6551 20150401; H01M
10/0525 20130101; Y02E 60/10 20130101 |
Class at
Publication: |
429/120 |
International
Class: |
H01M 10/50 20060101
H01M010/50 |
Foreign Application Data
Date |
Code |
Application Number |
Feb 20, 2007 |
JP |
2007-038880 |
Claims
1. A power supply apparatus wherein a liquid medium is housed so as
to provide an air layer in a first case which accommodates a power
supply unit, and when the liquid medium is heated to a temperature
higher than a vaporization temperature by external heat toward the
power supply unit, the liquid medium is vaporized to increase the
volume of the air layer to reduce heat conduction of the external
heat toward the power supply unit.
2. The power supply apparatus according to claim 1, wherein the
liquid medium is vaporized at a temperature lower than an upper
limit of a proper temperature range for the power supply unit.
3. The power supply apparatus according to claim 1, wherein a
heat-radiating fin is formed on an outer surface of the first
case.
4. The power supply apparatus according to claim 1, wherein the
first case includes a liquid housing portion which houses the
liquid medium and a guide surface which guides the liquid medium to
the liquid housing portion after the liquid medium is once
vaporized by the external heat and then changed into a liquid.
5. The power supply apparatus according to claim 1, wherein the
power supply unit includes a power supply portion and a second case
which accommodates a coolant, the coolant cools the power supply
portion, and the first case is in contact with an outer surface of
the second case.
6. The power supply apparatus according to claim 5, comprising: an
electromechanical energy converting element which is placed between
a vehicle heat-radiating portion for radiating heat in the power
supply unit to the outside of a vehicle and the second case and is
switched between a contact state in which the element is in contact
with the second case and the vehicle heat-radiating portion in
response to application of a voltage and a non-contact state in
which the element is not in contact with the second case and/or the
vehicle heat-radiating portion; and a control means for controlling
application of a voltage to the electromechanical energy converting
element.
7. The power supply apparatus according to claim 5, comprising: an
electromechanical energy converting element which is placed between
a vehicle heat-radiating portion for radiating heat in the power
supply unit to the outside of a vehicle and the second case and is
switched between a contact state in which the element is in contact
with the second case and the vehicle heat-radiating portion in
response to application of a voltage and a non-contact state in
which the element is not in contact with the second case and/or the
vehicle heat-radiating portion; and a control circuit for
controlling application of a voltage to the electromechanical
energy converting element.
Description
TECHNICAL FIELD
[0001] The present invention relates to a power supply apparatus
which includes a power supply unit therein.
BACKGROUND ART
[0002] Secondary batteries generate heat in charge and discharge
and suffer accelerated deterioration at a temperature higher than a
proper level. It is thus necessary to radiate heat thereof
smoothly. Patent Document 1 has disclosed a cooling system
described below as a method of promoting heat radiation in a
secondary battery.
[0003] The cooling system includes an assembled battery to be
cooled, A box which accommodates the assembled battery and is filed
with a coolant, a circulatory path through which the coolant is
ejected from the box and injected into the box, a pump which is
provided for the circulatory path to circulate the coolant through
the circulatory path, and a radiator which cools the coolant in the
circulatory path. When the assembled battery of this type is used
as a driving or auxiliary power supply in an electric car or a
hybrid car, the assembled battery can be fixed at a position where
favorable heat radiation is provided, for example, on a floor
panel.
[0004] With the abovementioned structure, when the assembled
battery in a vehicle generates heat in charge and discharge during
driving thereof, the assembled battery can be cooled with the
coolant cooled by the radiator.
[0005] [Patent Document 1] Japanese Patent Laid-Open No.
2003-346924
DISCLOSURE OF THE INVENTION
Problems to be Solved by the Invention
[0006] When the ignition is off in the vehicle to stop the
abovementioned cooling system, heat may be transferred from the
floor panel and applied to the assembled battery. This may
extremely increase the temperature of the assembled battery to
promote deterioration of the assembled battery.
[0007] It is an object of the present invention to prevent an
increase in temperature of a power supply unit due to external
heat.
Means for Solving Problems
[0008] To solve the abovementioned problem, the present invention
provides a power supply apparatus wherein a liquid medium is housed
so as to provide an air layer in a first case which accommodates a
power supply unit. When the liquid medium is heated to a
temperature higher than a vaporization temperature by external heat
toward the power supply unit, the liquid medium is vaporized to
increase the volume of the air layer to reduce heat conduction of
the external heat toward the power supply unit.
[0009] The liquid medium is vaporized at a temperature lower than
the upper limit of a proper temperature range for the power supply
unit. A heat-radiating fin may be formed on an outer surface of the
first case.
[0010] The power supply unit includes a power supply portion and a
second case which accommodates a coolant, the coolant cools the
power supply portion, and the first case is in contact with an
outer surface of the second case.
[0011] The first case includes a liquid housing portion which
houses the liquid medium and a guide surface which guides the
liquid medium to the liquid housing portion after the liquid medium
is once vaporized by the external heat and then changed into a
liquid.
[0012] The power supply apparatus includes an electromechanical
energy converting element which is placed between a vehicle
heat-radiating portion for radiating heat in the power supply unit
to the outside of a vehicle and the second case and is switched
between a contact state in which the element is in contact with the
second case and the vehicle heat-radiating portion in response to
application of a voltage and a non-contact state in which the
element is not in contact with the second case and/or the vehicle
heat-radiating portion, and a control means for controlling
application of a voltage to the electromechanical energy converting
element.
[0013] The power supply apparatus includes an electromechanical
energy converting element which is placed between a vehicle
heat-radiating portion for radiating heat in the power supply unit
to the outside of a vehicle and the second case and is switched
between a contact state in which the element is in contact with the
second case and the vehicle heat-radiating portion in response to
application of a voltage and a non-contact state in which the
element is not in contact with the second case and/or the vehicle
heat-radiating portion, and a control circuit for controlling
application of a voltage to the electromechanical energy converting
element.
Effects of the Invention
[0014] According to the present invention, when the liquid medium
is heated to a temperature higher than the vaporization temperature
by external heat toward the power supply unit, the liquid medium
can be vaporized to increase the volume of the air layer to reduce
heat conduction of the external heat toward the power supply unit.
It is thus possible to prevent an extreme increase in temperature
of the power supply unit due to the external heat.
BRIEF DESCRIPTION OF DRAWINGS
[0015] FIG. 1 A perspective view showing a passenger seat.
[0016] FIGS. 2A A section views illustrating the power supply
apparatus before a liquid medium is vaporized.
[0017] FIGS. 2B A section views illustrating the power supply
apparatus after part of the liquid medium is vaporized. Section
views showing a power supply apparatus.
[0018] FIG. 3 A block diagram for explaining application of a
voltage to a piezoelectric element in accordance with a battery
temperature.
[0019] FIG. 4 A flow chart illustrating a method of temperature
adjustment in the power supply apparatus.
[0020] FIG. 5 A section view showing the power supply apparatus
when a piezoelectric element is set in a contact state.
[0021] FIG. 6 A section view showing a power supply apparatus of
Modification 1.
[0022] FIG. 7 A section view showing a power supply apparatus of
Modification 2.
[0023] FIGS. 8A A section views showing a power supply apparatus
before a liquid medium is vaporized (Embodiment 2).
[0024] FIGS. 8B A section views showing a power supply apparatus
after part of the liquid medium is vaporized. (Embodiment 2).
DESCRIPTION OF REFERENCE NUMERALS
[0025] 2 POWER SUPPLY APPARATUS
[0026] 21 CYLINDRICAL ELECTRICAL CELL
[0027] 22 ASSEMBLED BATTERY
[0028] 23 COOLANT
[0029] 24 POWER SUPPLY CASE
[0030] 25 BRACKET
[0031] 26 PIEZOELECTRIC ELEMENT
[0032] 29 LIQUID MEDIUM
[0033] 30, 300 MEDIUM HOUSING CASE
[0034] 30a SECOND MEDIUM HOUSING CASE
[0035] 30b FIRST MEDIUM HOUSING CASE
[0036] 31 HEAT-RADIATING FIN
[0037] 300a INCLINED SURFACE
BEST MODE FOR CARRYING OUT THE INVENTION
[0038] Preferred embodiments of the present invention will
hereinafter be described.
Embodiment 1
[0039] FIG. 1 is a perspective view showing a passenger seat 11 of
a vehicle. The passenger seat 11 has a seat 12 and a back rest 13.
A head rest 14 is removably attached to the top end of the back
rest 13. A pair of seat rails 15 is provided under the seat 12 to
extend in a front-to-back direction and opposite to each other in a
width direction.
[0040] Each of the seat rails 15 is formed of a lower rail 15a
fixed onto a floor panel (vehicle heat-radiating portion) 16 and an
upper rail 15b fixed to a lower surface of the seat 12. The upper
rail 15b is slidable over the lower rail 15a in a longitudinal
direction thereof and is guided by the lower rail 15a. The seat
rails 15 allow adjustments of the position of the passenger seat 11
in the front-to-back direction of the vehicle.
[0041] A power supply apparatus 2 is provided between the paired
seat rails 15. The power supply apparatus 2 is fixed to the floor
panel 16 and is used as a driving power source of a hybrid
vehicle.
[0042] Next, the configuration of the power supply apparatus 2 will
be described with reference to FIGS. 1 and 2. FIGS. 2A and 2B are
section views illustrating the power supply apparatus 2, in which
FIG. 2A shows the apparatus 2 before a liquid medium is vaporized
and FIG. 2B shows the apparatus 2 after part of the liquid medium
is vaporized.
[0043] In FIGS. 2A and 2B, the power supply apparatus 2 includes an
assembled battery (power supply portion) 22 which includes a
plurality of cylindrical electrical cells 21 arranged in parallel,
a coolant 23 which cools the assembled battery 22, and a power
supply case (second case) 24 which accommodates the assembled
battery 22 and the coolant 23. A lithium-ion battery can be used as
each of the cylindrical electrical cells 21.
[0044] The lithium-ion battery is increasingly deteriorated at a
battery temperature higher than 60.degree. C. and cannot provide a
sufficient output at a battery temperature lower than 25.degree. C.
For this reason, the battery temperature of each of the cylindrical
electrical cells 21 is preferably adjusted to fall within a range
from 25 to 60.degree. C. (proper temperature range). Each of the
cylindrical electrical cells 21 may be formed of a nickel metal
hydride (NiMH) battery instead. The proper temperature range
described in claims refers to a range of battery temperatures
required to prevent significant progress of deterioration and to
provide a battery output corresponding to a needed output level.
The proper temperature range can be changed as appropriate
depending on the type of the battery.
[0045] Suitable materials for the coolant 23 for the assembled
battery 22 include one that has a high specific heat, a high
thermal conductivity, and a high boiling point, does not corrode
the power supply case 24 or the assembled battery 22, and has
resistance to thermal decomposition, air oxidation, and
electrolysis. An electrical insulating liquid is desirable to
prevent short-circuit between electrode terminals. For example, a
fluorine-containing inert liquid can be used. Examples of the
fluorine-containing inert liquid may include Fluorinert
manufactured by 3M, Novec HFE (hydrofluoroether), and Novec1230. A
liquid other than the fluorine-containing inert liquid may be used
(for example, silicone oil).
[0046] The power supply case 24 is formed of a case upper-wall
portion 24a, a case side-wall portion 24b, and a case lower-wall
portion 24c. The case side-wall portion 24b and the case lower-wall
portion 24c are integrally formed, while the case upper-wall
portion 24a is formed as a separate component from the case
side-wall portion 24b and the case lower-wall portion 24c.
[0047] The case upper-wall portion 24a is formed in a pyramidal
shape with its portions inclined downward outwardly in a horizontal
direction of the power supply case 24.
[0048] A medium housing case (first case) 30 which accommodates a
liquid medium 29 in part thereof is attached to an outer surface of
the power supply case 24 (except for an outer surface of the case
lower-wall portion 24c). The medium housing case 30 is formed of a
first medium housing case portion(liquid housing portion) 30b on
the periphery of the case side-wall portion 24b and a second medium
housing case portion 30a on the periphery of the case upper-wall
portion 24a. The medium housing case 30 is in contact with the case
upper-wall portion 24a and the case side-wall portion 24b to hold
the power supply case 24. The first and second medium housing cases
30b and 30a communicate with each other.
[0049] The first medium housing case portion 30b accommodates the
liquid medium 29. The liquid medium 29 surrounds generally the
assembled battery 22 in the horizontal direction before the liquid
medium 29 is vaporized (see FIG. 2A).
[0050] An air layer (gas layer) is provided in part of the first
medium housing case portion 30b (in an area above the liquid level
of the liquid medium 29) and in the second medium housing case
portion 30a. The liquid medium 29 can be realized by using a
fluorine-containing inert liquid and is vaporized when the liquid
temperature reaches 55.degree. C. under atmospheric pressure.
[0051] The medium housing case 30 may have a volume set such that
part of the liquid medium 29 can be vaporized as shown in FIG. 2B
or all the liquid medium 29 can be vaporized.
[0052] The wall portion of the second medium housing case portion
30a closer to the power supply case 24 is inclined downward
outwardly in the horizontal direction of the power supply case 24
similarly to the case upper-wall portion 24a. Thus, after the
liquid medium 29 is once vaporized in the first medium housing case
portion 30b and cooled in the second medium housing case portion
30a to be changed into liquid form, the liquid medium 29 can be
returned to the first medium housing case portion 30a along the
wall portion of the second medium housing case portion 30b by
gravity.
[0053] A plurality of heat-radiating fines 31 are formed on an
outer surface of the medium housing case 30. The heat-radiating
fins 31 increase the area in contact with outside air to promote
heat radiation of the power supply apparatus 2. This allows the
once vaporized liquid medium 29 to be returned to a liquid state
readily.
[0054] A bracket 25 for fixing the power supply apparatus 2 to the
floor panel 16 is provided on a lower surface of the medium housing
case 30. The bracket 25 can support the power supply apparatus 2 at
a position separated from the floor panel 16. The bracket 25 may be
formed of resin, for example.
[0055] A piezoelectric element (electromecanical energy converting
element) 26 is provided between the case lower-wall portion 24c and
the floor panel 16 and is fixed onto the floor panel 16. The
piezoelectric element 26 may be formed of a conductive polymer or
an electrostriction elastomer, for example.
[0056] The piezoelectric element 26 is provided with electrode
portions 26a on both end faces in a vertical direction (on surfaces
in contact with the case lower-wall portion 24c and the floor panel
16). The electrode portions 26a are electrically connected to a
direct-current element power supply 54 for applying a voltage to
the piezoelectric element 26 (see FIG. 3). The application of a
voltage to the piezoelectric element 26 by the element power supply
54 is controlled by an element power supply control circuit 55.
[0057] As shown in FIG. 3, the element power supply control circuit
55 controls the application of a voltage based on information
(temperature information) output from a temperature sensor 56
provided for the assembled battery 22.
[0058] When no voltage is applied to the piezoelectric element 26
by the element power supply 54, the piezoelectric element 26 is
separated from the power supply case 24 as shown in FIGS. 2A and 2B
(hereinafter referred to as a non-contact state). When a voltage is
applied to the piezoelectric element 26 in the non-contact state,
the piezoelectric element 26 is extended in the vertical direction
and brought into contact with the power supply case 24 as shown in
FIG. 5 (hereinafter referred to as a contact state).
[0059] The piezoelectric element 26 includes an insulating filler
(for example, aluminum nitride or aluminum oxide). The insulating
filler can increase the heat conductivity of the piezoelectric
element 26 to promote heat radiation from the assembled battery 22
to the floor panel 16.
[0060] Next, the method of cooling the assembled battery 22 will be
described in the respective cases where the ignition is off and
where the ignition is on in the vehicle.
When Ignition is Off in Vehicle
[0061] When the ignition is off in the vehicle and the vehicle is
parked under a high-temperature environment (for example, when the
vehicle is parked in a parking area exposed to direct sunlight),
heat may be transferred from the floor panel 16 to increase the
temperature of the assembled battery 22 to a level above the upper
limit of the proper temperatures.
[0062] The proper temperatures range from 25.degree. C. to
60.degree. C. for lithium-ion batteries as described above. If a
fan (not shown) is provided for cooling the power supply apparatus
2, it is assumed that the fan is stopped in response to the
turn-off of the ignition in the vehicle (that is, the cooling means
for the power supply apparatus 2 is not operated).
[0063] When the ignition is off in the vehicle and the vehicle is
parked under a low-temperature environment (for example, when the
vehicle is parked in a cold climate region with heavy snow), the
cold air may flow into the assembled battery 22 through the floor
panel 16 (that is, the heat may escape from the assembled battery
22 through the floor panel 16) to reduce the temperature of the
assembled battery 22 to a level below the lower limit of the proper
temperatures.
[0064] To address these problems, when the ignition is off in the
vehicle, the piezoelectric element 26 is separated from the power
supply case 24 to form the air layer between the floor panel 16 and
the power supply case 24. The air layer can prevent transfer of
heat from the outside of the vehicle to the assembled battery 22
through the floor panel 16 and can prevent flowing of heat in the
assembled battery 22 to the outside of the vehicle through the
floor panel 16.
[0065] When the vehicle is parked under a high-temperature
environment and heat in the interior of the vehicle flows into the
liquid medium through the heat-radiating fins 31 and the like to
increase the temperature of the liquid medium 29 to 55.degree. C.,
part of the liquid medium 29 is vaporized (see FIG. 2B). This can
remove the heat flowing into the medium housing case 30 through the
evaporation cooling.
[0066] The vaporization of part of the liquid medium 29 can drop
the liquid level of the liquid medium 29 to increase the volume of
the gas layer in the first medium housing case portion 30b. This
can reduce the amount of the heat flowing into the power supply
case 24 as compared with the amount before the liquid medium 29 is
vaporized, thereby preventing an extreme increase in temperature of
the assembled battery 22.
[0067] Since the air layer is present in the second medium housing
case portion 30a at all times, it can prevent external heat from
flowing into the power supply case 24 from above the power supply
apparatus 2.
[0068] The vaporized liquid medium 29 is cooled mainly through the
heat-radiating effect of the heat-radiating fins 31 and is returned
to a liquid state when the temperature is reduced below 55.degree.
C. The liquid medium 29 changed into the liquid state is moved by
gravity along an inclined surface (guide surface) 300a formed on an
inner surface of the second medium housing case portion 30a and
flows into the first medium housing case portion 30b. Then, the
liquid medium 29 can be reused.
When Ignition is On in Vehicle
[0069] Next, the method of temperature adjustment in the power
supply apparatus 2 will be described when the ignition is on in the
vehicle with reference to FIG. 4 which is a flow chart showing the
method of temperature adjustment in the power supply apparatus 2.
The flow chart is performed by the element power supply control
circuit 55 which continuously monitors the temperature information
output from the temperature sensor 56. The piezoelectric element 26
is separated from the power supply case 24 in the initial
state.
[0070] First, it is determined whether or not the temperature of
the assembled battery 22 is higher than a threshold value
(60.degree. C.) based on the temperature information from the
temperature sensor 56 (step S101).
[0071] When the temperature of the assembled battery 22 is higher
than 60.degree. C., a voltage is applied to the piezoelectric
element 26 to change the piezoelectric element 26 from the
non-contact state to the contact state as shown in FIG. 5 (step
S102). If the temperature of the liquid medium 29 is equal to or
higher than 55.degree. C. at this point, the volume of the air
layer in the medium housing case 30 is increased. Thus, the heat in
the assembled battery 22 is mainly escaped toward the floor panel
16 through the piezoelectric element 26.
[0072] On the other hand, if the temperature of the liquid medium
29 is lower than 55.degree. C., the heat in the assembled battery
22 is escaped toward the floor panel 16 and the heat-radiating fins
31 through the piezoelectric element 26 and the liquid medium
29.
[0073] When the temperature of the assembled battery 22 is reduced
to 60.degree. C. or lower (step S103), the application of the
voltage to the piezoelectric element 26 is stopped (step S104) to
move the piezoelectric element 26 set in the contact state to the
non-contact state.
[0074] According to the abovementioned method of temperature
adjustment, the temperature of the assembled battery 22 can be
maintained in the proper range, so that the life of the assembled
battery 22 can be extended.
Modifications
[0075] While the piezoelectric element 26 is used to perform
control for switching the floor panel 16 and the power supply case
24 between the contact state and the non-contact state in the
embodiment described above, a thermo-sensitive deformable element
may be used instead. In this case, the thermo-sensitive deformable
element which is deformed at a predetermined temperature (for
example, 60.degree. C.) may be fixed to the power supply case 24
without any contact with the floor panel 16. When the temperature
of the power supply case 24 reaches 60.degree. C., the
thermo-sensitive deformable element is deformed and brought into
contact with the floor panel 16 to allow radiation of heat in the
assembled battery 22.
[0076] It is also possible to provide a pressure adjusting portion
which adjusts the pressure in the medium housing case 30. If the
assembled battery 22 of a different type is used, the vaporization
temperature of the liquid medium 29 can be easily changed depending
on the proper temperatures of that assembled battery 22 with the
pressure adjustment by the pressure adjusting portion.
[0077] A gas discharge valve may be provided for the medium housing
case 30. The gas discharge valve may be a rupture-type valve formed
by partially thinning the wall portion of the medium housing case
portion 30b or may be a spring-type self-returning valve.
[0078] The rupture-type valve can be broken to release the internal
pressure of the medium housing case 30 to the outside of the power
supply apparatus 2 if the internal pressure of the medium housing
case 30 is increased.
[0079] The spring-type self-returning valve can be formed by
movably providing a movable valve in an opening formed in the wall
portion of the medium housing case 30 and attaching a spring to the
movable valve.
[0080] If the internal pressure of the medium housing case 30 is
increased, the movable valve can be retracted from the opening
against the spring force of the spring to allow release of the
pressure inside the medium housing case 30 through the opening. If
the internal pressure of the medium housing case 30 is reduced, the
movable spring is returned into the opening by the spring force of
the spring. In this manner, an extreme increase in internal
pressure of the medium housing case 30 can be prevented.
[0081] Alternatively, the power supply apparatus 2 can be formed as
shown in FIG. 6 which is a section view showing Modification 1 of
the power supply apparatus 2. A first medium housing case portion
30b is formed only partially on an outer surface of a case
side-wall portion 24b. It should be noted that the specification is
interpreted such that the medium housing case 30 holds the power
supply case 24 including the case where the medium housing case 30
is in contact with part of the outer surface of the power supply
case 24.
[0082] Alternatively, the power supply apparatus 2 can be formed as
shown in FIG. 7 which is a section view showing Modification 2 of
the power supply apparatus 2. A case upper-wall portion 24a of a
power supply case 24 is not in contact with a second medium housing
case portion 30a. A first medium housing case portion 30b is in
contact with the whole outer surface of a case side-wall portion
24b of the power supply case 24. A plurality of heat-radiating fins
31 are formed on the case upper-wall portion 24a.
[0083] Since external heat at a high temperature is moved upward,
such a structure can be used when a small amount of external heat
flows through the case upper-wall portion 24a. This allows
efficient radiation of heat in the assembled battery 22 by using
the heat-radiating fins 31 formed on the case upper-wall portion
24a when the assembled battery 22 should be cooled.
[0084] Alternatively, the distribution of temperature in the
assembled battery 22 in charge and discharge may be previously
measured and the piezoelectric element 26 may be placed only in an
area corresponding to an area (or a plurality of areas) at a high
temperature.
[0085] The piezoelectric element 26 may be fixed to the power
supply case 24, or the piezoelectric element 26 may be supported
between the power supply case 24 and the floor panel 16 (that is,
the piezoelectric element 26 is not in contact with the power
supply case 24 or the floor panel 16), and is brought into contact
with both the power supply case 24 and the floor panel 16 when heat
radiation is performed.
[0086] While the power supply apparatus 2 is placed under the
passenger seat 11, it can be placed in a console box between seats,
under a backseat, in a trunk room or the like.
Embodiment 2
[0087] Next, Embodiment 2 of the present invention will be
described with reference to FIGS. 8A and 8B which are section views
showing a power supply apparatus of Embodiment 2. FIG. 8A shows the
apparatus before a liquid medium 29 is vaporized and FIG. 8B shows
the apparatus after part of the liquid medium 29 is vaporized.
Portions identical to those of Embodiment 1 are designated with the
same reference numerals.
[0088] A medium housing case (first case) 300 is placed to surround
the whole outer surface of a power supply case 24. The liquid
medium 29 is stored in a bottom portion of the medium housing case
300.
[0089] The liquid level of the liquid medium 29 before the
temperature reaches a vaporization temperature is set to the same
level as that of a case lower-wall portion 24c. In this case, since
the liquid medium 29 is in contact with the case lower-wall portion
24c, heat exchange can be performed between the power supply case
24 and a floor panel 16 through the liquid medium 29.
[0090] On the other hand, when part of the liquid medium 29 is
vaporized to reduce the liquid level as shown in FIG. 8B, an air
layer is formed between the case lower-wall portion 24c and the
liquid medium 29. The formed air layer (gas layer) prevents heat
exchange between the power supply case 24 and the floor panel
16.
[0091] Next, the method of cooling an assembled battery 22 will be
described in the respective cases where the ignition is off and the
ignition is on in the vehicle.
When Ignition is Off in Vehicle
[0092] When the ignition is off in the vehicle and the vehicle is
parked under a high-temperature environment (for example, when .the
vehicle is parked in a parking area exposed to direct sunlight),
external heat maybe transferred from the floor panel 16 to vaporize
part of the liquid medium 29 stored in the bottom portion of the
medium housing case 300 (see FIG. 8B).
[0093] The external heat flowing into the power supply case 24
through the floor panel 16 is cooled through evaporation cooling,
and the lowered liquid level of the liquid medium 29 forms the air
layer between the case lower-wall portion 24c and the liquid medium
29. The air layer can prevent transfer of the heat in the floor
panel 16 to the power supply case 24.
When Ignition is On in Vehicle
[0094] When the vehicle is parked in a high-temperature
environment, the air layer formed between the case lower-wall
portion 24c and the liquid medium 29 at the start of driving of the
vehicle prevents escape of the heat in the assembled battery 22 to
the floor panel 16.
[0095] It is contemplated, however, that the temperature of the
floor panel 16 is gradually reduced through air cooling associated
with the driving of the vehicle to return the vaporized liquid
medium 29 to a liquid state. Thus, if the assembled battery 22
generates heat during the driving of the vehicle, the heat in the
assembled battery 22 can be escaped toward the floor panel 16
through the liquid medium 29.
* * * * *